1. Technical Field
This invention relates to electronic circuit designs for high density column drivers for an active matrix (thin-film transistor) liquid crystal display.
2. Description of Related Art
With recent progress in various aspects of active matrix (thin-film transistor) liquid crystal display (LCD) technology, the proliferation of active matrix displays has been spectacular in the past several years. In an active matrix display, there is one transistor or switch corresponding to each display cell. An active matrix display is operated by first applying a selection voltage to a row electrode to activate the gates of that row of cells, and second applying appropriate analog data voltages to the column electrodes to charge each cell in the selected row to a desired voltage level.
Column drivers are very important circuits in the design of an active matrix display panel. The column drivers receive digital display data along with control and timing signals from a display controller chip. The column drivers convert the digital display data to analog display voltages, typically using one CMOS-based circuit per column to perform the conversion. The column drivers then output the analog display voltages onto column electrodes of the display.
As the resolution of LCD flat panel displays (FPDs) increases, the layout area typically required by the column driver circuits increases dramatically. For example, as the resolution of an LCD FPD increases from 6 bits per primary color (for a total of about 256 thousand colors possible) to 8 bits per primary color (for a total of about 16 million colors possible), the layout area typically required increases by a factor of four (due to the two additional bits of shading per primary color).
To alleviate the above described problem, a new circuit and layout scheme for LCD column drivers is needed.